In this problem, we are given the equations of the two sides of a rhombus.
Equation 1 is 4 x – 10
Equation 2 is 2 x + 20
Since the given shape is a rhombus, therefore the two sides have equal sides. Hence, we can simply equate equation 1 and equation 2:
4 x – 10 = 2 x + 20
2 x = 30
x = 15
Therefore the answer is:
A. 15